Berosus pallidipennis ( Sharp, 1884 )

Seidel, Matthias, Sýkora, Vít, Leschen, Richard A. B. & Fikáček, Martin, 2021, A review of the New Zealand Berosus (Coleoptera: Hydrophilidae) with descriptions of three new species, Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) 61 (1), pp. 243-252 : 244-248

Berosus pallidipennis ( Sharp, 1884)

( Figs 1A, E ; 2A, E–F )

Phelerosus pallidipennis Sharp, 1884: 480 . Transferred to Berosus by Kඇංඌർπ (1924).

Berosus mergus Broun, 1886: 883 . Synonymized by d’Oඋർπඒආඈඇඍ (1937).

Type material examined. Berosus pallidipennis : Lൾർඍඈඍඒඉൾ (hereby designated): J ( BMNH): “ ♀ / Phelerosus / pallidipennis / Type D. S. / Dunedin. N. Zd. / Thomson // Sharp Coll. / 1905-313. // TYPE / H.T. // SYN- / TYPE ”. Pൺඋൺඅൾർඍඈඍඒඉൾඌ: 1 J 1 ♀ ( BMNH): “ ♀ J / Phelerosus / pallidipennis. / Greymouth. n.3. / Helms. 1883. // Greymouth, / New Zealand. / Helms. // Sharp Coll. / 1905-313. // SYN- / TYPE ”.

Berosus mergus : Lൾർඍඈඍඒඉൾ (hereby designated): J ( BMNH): “Maungatua // 1572 // Berosus / mergus // New Zealand / Broun Coll. / Brit. Mus. / 1922-482. // Type ”.

Additional material examined. Adults. NEW ZEALAND: NඈඋඍΗ Iඌඅൺඇൽ: 1 spec. ( NZAC): T. Broun lgt. Bay of Plenty: 1 spec. ( NZAC): Te Rereauira Stream, Ditch near Melicytus swamp, 24.xi.1992, M. C. Lariviere lgt.; 2 spec. ( NZAC): Te Araroa Rd, Mangaomeko Stream, 37.59162°S, 178.21096°E, 50 m, 23.i.2017, water collecting, Leschen & Maier leg., NZ17-0123-CM1; 1 spec. ( FMNH): E of Opotiki, Opape Beach Road, unnamed stream, 37.97854°S, 177.42752°E, 30 m, 24.i.2017, water collecting, Leschen & Maier leg., NZ17-0124-CM2. Gisborne: 1 spec. ( NZAC): near Mangatiti Bridge, Waiorongomai River, 37.8641°S, 178.1892°E, 22.i. 2017, 128 m, from flood debris, Leschen & Maier leg., NZ17-0122-CM1. Hawkes Bay: 1 spec. ( NZAC):Dartmoor, Mangaone, 28.i.1959, B. M. May lgt.; 1 spec. ( NZAC): Maraekakaho, 22.xi.1966, R. M.Bull lgt.; 1 spec. ( NZAC):Waipatiki, 27.i.1959, B. M. May lgt.; 2 spec. ( EMEC): N of Waipukurau,Tukituki River, 39°59.31′S, 176°33.52′E, 122 m, 20.ii.2016,W.D.Shepard leg.,WDS-A-2003. Rangitikei: 1J ( NZAC): Makiekie stream, Makoura road, 15.ii.1997; 1 spec. ( NMPC): Ruahine Forest Park, Waipawa River S of Triplex hut, 39.8055°S, 176.19245°E, 600 m 26.xi.2016, stony stream with bare gravel banks, flowing from Nothofagus -podocarp forest: stream collecting, in side pools and submerged gravel with decaying leaves, Fikáček & Seidel lgt. MM29. Waikato: 3 spec. ( NZAC): Rararimu Stream, 4.iii.2012, at large, 38°23.048′S, 174°44.212′E, M. Gimmel, R. Leschen, RL1671; 1 spec. ( NMPC): Ruahoanga Scenic Reserve at Honikiwi Rd., 70 m, 38.1579°S, 175.0684°E, 16.xi.2017, in exposed muddy pools at sides of the road and on the track in Ruahoanga Reserve, partly vegetated, Fikáček, Sadílek & Sýkora lgt. Wairarapa: 1 spec. ( NZAC): Martinborough, 26.xii.1917, A. C. O’Connor & A.E. Brookes lgt. Wanganui: 1 spec. ( NZAC):Manawatu, Grasslands, 9.i.1952; 1 spec. ( NZAC): Palmerston North, 5.xi.1961, C. Laurie & G. Laurie lgt.; 2 spec. ( NZAC):Palmerston North, 20.i.1939, M. J. Esson lgt.; 4 spec. ( EMEC, NMPC): Bulls, 40°11.17′S 175°23.47′E, 9.ii.2016, 33 m, pools near river, W. D. Shepard. leg., WDS-A-1988A; 1 spec. ( EMEC): Bulls, 40°11.17′S, 175°23.47′E, 33 m, 9.ii.2016, W. D. Shepard leg., pools near river, WDS-A-1988A. Wellington: 1 spec. ( NZAC): Otaki Forks, Waiotauru River, 30.xii.1980, J. Nunn lgt.; 2 spec. ( NZAC): Wellington, Hutt River, 2.i.1928, A. E. Brookes lgt.; 1 ♀ ( BMNH): Wellington, Hutt River, 2.i.1928. Taupo: 2 spec. ( NMPC): 7.5km SSE of Murupara, Mangawiri Bridge No. 184, 260 m, 22.xi.2012, 38°30.9′S, 176°44.1′E, Becker, Fikáček & Hájek lgt., NZ01. SඈඎඍΗ Iඌ- අൺඇൽ: Buller: 4 spec. ( NZAC): Kawatiri, Hope River, 2.ii.2000, P. Cranston lgt.; 7 spec. ( NZAC): Mawhera S. F., Wallaby Creek, BFUP, 9.i.1973, J. C. Watt lgt.; 1 spec. ( NMPC):Lake Rotoiti, road to Mt.Robert, 42°47.82′S 172°49.68′E, 3.xii.2010,under rocks and along margin of small lake, Fikáček & Leschen leg, RL1535; 9 spec. ( NMPC, NZAC): Little Grey River at road bridge 0.5 km S of Mawheraiti, water collecting in small exposed river: collecting in gravel, on stones and in side pools 42°11.91′S, 171°43.26′E, 140 m, 25.ii.2016, Seidel, Sýkora, Leschen, Maier & Lambert lgt., 2016-NZ-MS76; 1 spec. ( NMPC): Nelson Lakes NP, St. Arnaud small lake at N end of Lake Rotoiti, 632 m, 41.7992°S, 172.8233°E, 5.xii.2016, water collecting in a small lake in the shruby area, Fikáček & Seidel lgt. MM55. Central Otago: 1 spec. ( NMPC):Little Kye Burn at Danseys Pass Road bridge, 45°02.63′S, 170°15.21′E, 480 m, 16.ii.2016, water collecting in small river among pastures: collecting in gravel and submerged vegetation, Seidel, Sýkora, Leschen & Maier lgt., 2016-NZ-MS16. Dunedin: 5 spec. ( NMPC, NZAC, ZMH): 6 km W of Waitaki Bridge, Waitaki Riverbed, S44°55.2′, E171°01.5′, 35 m, J. Hájek & P. Hlaváč lgt.; 20 spec. ( NMPC, NZAC): Silver Stream Valley Rd. at Silver Stream, 45°48.71′S, 170°25.07′E, 95 m, 11.ii.2016, moderately large exposed polluted stream at partly degraded forest area, Seidel, Sýkora & Fikáček lgt., 2016-NZ072. Fiordland: 6 spec. ( NMPC, NZAC): Monowai Lookout Tk at Monowai campsite, 45°48.67′S 167°31.21′E, 210 m, 26–28.i. 2016 in submerged grasses and gravel banks of the wetland at the end of Lake Monowai,Seidel, Sýkora & Fikáček,2016-NZ030; 1 spec. ( NMPC): Pig Creek at Borland Road, 45°46.49′S, 167°32.01′E, 180 m, 31.i.2016, peaty forest stream with stony streambed flowing from Nothofagus forest, Seidel & Sýkora lgt., 2016-NZ045; 1 spec. ( NMPC): at Borland Rd. 1.7 km W of Monowai, 45°46.72′S, 167°35.68′E 160 m, 26.i.2016, stream collecting: slow-flowing exposed gravel stream among pastures, V. Sýkora lgt., 2016-NZ029. Kaikoura: 28 spec. ( EMEC, NMPC):S of Mt.Lyford Village, Wandle River, 42°35.21′S, 173°05.99′E, 229 m, 18.ii.2016, W. D. Shepard leg., WSD-A-2000; 42 spec. ( NMPC, NZAC, ZMH): Kahutara River at Inland Kaikoura Road, 42°23.07′S, 173°26.96′E, 181 m, 29.xi.2017,water collecting in small exposed puddles without vegetation in wide riverbed, Fikáček, Sadílek & Sýkora lgt. Marlborough: 4 spec. ( NZAC): Pelorus Bridge, 7.viii.1957, J. I. Townsend lgt.; 5 spec. ( NZAC): Pelorus Bridge, 7.xi.1957, M. J. Esson lgt.; 1 ♀ ( NMPC):Stoney Creek, 42°42.95′S, 173°4.86′E, 3.xii.2010, along margins and under rocks in stream, Fikáček & Leschen leg., RL1537; 13 spec. ( NZAC):Pelorus River, 9.xii.2018, gravel bar, 41°17.966′S, 173°34.780′E, R Leschen,V.Sýkora, RL2084; 1 spec. ( NMPC):Stoney Creek, 3.xii.2010, M. Fikáček, R. Leschen, RL1537; 41 spec. ( NMPC, NZAC, ZMH): Pelorus Bridge Scenic Reserve Pelorus River at Totara Path, 41.30012°S, 173.57582°E, 35 m 11.xii.2016, water collecting in Pelorus River: in submerged gravel + in flooded vegetation at sandy/clayey steep banks and rocks, M. Fikáček & M. Seidel lgt. MM69c. Mid Canterbury: 1 ♀ ( NZAC): Mt Algidus, 3.xii.1913, T. Hall & A. E. Brookes lgt.; 1 J 2 ♀♀ ( NZAC): Mt Somers, 1500 m, 17.i.1964, M. J. Esson & J. I. Townsend lgt.; 1 spec. ( NZAC): Lincoln, Coes Ford, 20.i.1970, Ento. Dept Field Trip; 1 J ( NZAC): Ashley Gorge, river bed, 31.i.1994; 1 ♀ ( NZAC): Mount Hutt Forest, 26.xii.1997; 2 JJ 3 ♀♀ ( NMPC): Rangitata River at Rangitata Gorge Road,Ashburton Lakes, 415 m, 16.xii.2018, huge exposed river and its side arms in enormous riverbed, R. Leschen & V.Sýkora lgt., 2018-NZ97. North Canterbury: 4 J J 6 ♀♀ ( NZAC): Waitohi River at bridge, Medbury Road W of Medbury; 42.8782778°S 172.6509444°E; 253 m; 14.xii.2018, R. Leschen & V. Sýkora, RL2103; 1 ♀ ( NMPC): 22.8 S of Lewis Pass, Boyle River at Windy Point, 515 m, 42.58546°S, 172.37549°E 8.xii.2016, in isolated rocky pools with sandy bottom on the cliffs above Boyle River next to the hanging bridge,Fikáček & Seidel lgt. MM64. Nelson: 2 spec. ( NZAC): Buller River, T. Broun & A. E. Brookes lgt.; 10 spec. ( NZAC): Tapawera, 23.i.1962, E. S. Gourlay lgt.; 4 spec. ( NZAC): Wangapeka Valley, 2.xii.1934, E. S. Gourlay lgt.; 1 spec. ( NZAC): Takaka River at Lindsays Bridge, Uruwhenua, 40.9877889°S 172.819775°E, 80 m, 2.xii.2018, R. Leschen & V. Sýkora, RL2046; 1 spec. ( NZAC): St.Arnaud, Nelson Lakes, i.1977, M. J. Meads lgt.; 1 spec. ( NZAC): Lake Tennyson, 22.i.1977, M. J. Meads lgt. Otago Lakes: 2 JJ 2 ♀♀ ( BMNH): Paradise, 10.i.1945, C. E. Clark lgt.; 11 spec. ( EMEC, NMPC): Te Anau, Hwy 94, unnamed stream, 45°24.52′S, 167°44.36′E, 221 m, 14.ii.2016, W. D. Shepard leg., 11 spec. ( EMEC, NMPC): OL, Te Anau, Hwy 94, unnamed stream, 45°24.52′, 167°44.36′, 221 m, 14.ii.2016, WDS-A-1996, W. D. Shepard leg.; 17 spec. ( NMPC, NZAC):Pool at Wanaka Mount Aspiring Road, 44°30.30′S, 168°46.00′E, 348 m, 2.xii.2017, water collecting in small stony pool on side of the road, Fikáček, Sadílek & Sýkora lgt. South Canterbury: 1 spec. ( EMEC): St. Andrews, Hwy 1, unnamed river, 44°29.665′S, 171°11.962′S, 17.ii.2016, W. D. Shepard leg.; 7 spec. ( NMPC, NZAC): Peel Forest Reserve, 9. ii.2016, pasture pool, 43°53.9′S 171°13.8′E, 400 m, J. Hájek & P. Hlaváč lgt. Southland: 1♀ ( BMNH):Invercargill,Thomsons Bush, flood debris, 27.i.1984, P. M. Hammond; 23 spec. ( NMPC, NZAC):Whitestone River at Hillside Manapouri Rd. 13.2 km S of Te Anau, 45°31.67′S, 167°45.36′E, 230 m, 28.i.2016, large river in stony/gravelly riverbed:collecting in river + in gravel banks and isolated pools with submerged vegetation, Seidel, Sýkora & Fikáček lgt., 2016-NZ035; 4 spec. ( NMPC, NZAC): Redcliff Creek at Blackmount-Redcliff Rd., 14.5 km SSE of Manapouri, 45°41.69′S, 167°39.27′E, 200 m, 28.i.2016, exposed moderately large stony stream, Seidel, Sýkora & Fikáček lgt., 2016-NZ034; 16 spec. ( NMPC): Wairaki River 13 km N of Clifden, 45°56.05′S, 167°42.33′E, 90 m, 23.i.2016, small river in a wide gravel riverbed: water collecting in gravel, small rapids, in submerged plants at side of the rived and in isolated pools in the riverbed, Seidel, Sýkora & Fikáček lgt., 2016-NZ019; 2 spec. ( NMPC): Mataura River at Waikaia Rd. 3.7 km N of Riversdale, 45°52.20′S, 168°45.54′E, 130 m, 7.ii.2016, in large river in gravel riverbed:in the river,in side pools on gravel banks, among submerged vegetation, Seidel, Sýkora & Fikáček lgt., 2016-NZ066; 1 spec. ( NMPC): Steeple Flat at Piano Flat Rd., 45°40.55′S, 168°52.86′E, 180 m, 7.ii.2016, exposed stony stream among pastures + isolated side pools in gravel river-bed, Seidel, Sýkora & Fikáček lgt. 2016-NZ065; 3 spec. ( NMPC): Ligar Creek at Lake Monowai Rd., 45°47.35′S, 167°38.86′E, 140 m, 26.i.2016, stream collecting in large stream with gravel-stony banks, Seidel, Sýkora & Fikáček lgt., 2016- NZ031. Westland: 13 spec. ( NMPC, NZAC):Pegleg Creek at Otira Hwy., collecting in medium-sized partly exposed forest stream, 42°53.70′S, 171°33.57′E, 830 m, 24.ii.2016, Seidel, Sýkora, Leschen, Maier & Lambert lgt., 2016-NZ-MS69; 11 spec. ( NMPC, NZAC): Mount Aspiring NP, Pleasant Flat 27.2 km NNE of Makarora, at Mur Creek, 120 m, 11.xii.2012, 44°0.8′S 169°22.9′E, Fikáček, Hájek & Leschen lgt., NZ49.

Larvae. NEW ZEALAND: SඈඎඍΗ Iඌඅൺඇൽ:North Canterbury: 8 larvae ( NMPC):S of Mt.Lyford Village,Wandle River, 42°35.21′S, 173°05.99′E, 229 m, 18.ii.2016, W. D. Shepard leg., WSD-A-2000; 1 larva ( NMPC): Wairaki River 13 km N of Clifden, 45°56.05′S, 167°42.33′E, 90 m, 23.i.2016, small river in a wide gravel riverbed:water collecting in gravel, small rapids, in submerged plants at side of the rived and in isolated pools in the riverbed, Seidel, Sýkora & Fikáček lgt., 2016- NZ 019.

Redescription of adult. Body length 3.7–4.8 mm. Shape ellipsoid, moderately elongate ( Figs 2A, E ).

Coloration. Labrum black with green and/or purple metallic reflections, dorsum of head black with varying degrees of metallic green or purple reflections. Pronotal ground coloration yellowish, bearing large rectangular dark metallic spot covering nearly whole surface except wide lateral and anterior margins. Scutellar shield with same color as head. Elytra testaceous with brown punctures. Ventral surface pitch-black. Maxillary palpi with palpomere 4 darkened in apical half. Legs with trochanters and basal half of femora black, other parts testaceous. Antennae testaceous.

Dorsum. Head densely punctate, punctures on clypeus 1.5–2.0 times as large as ommatidia, regularly spaced; punctures on frons 2.0–3.0 times as large as ommatidia, irregular, getting contiguous towards eyes. Pronotal punctures dense and coarse, getting denser towards lateral margins with punctures on disc about the same size as those on frons. Pronotal surface without apparent setae. Scutellar shield coarsely punctate with smooth lateral margins. Elytral striae well-impressed, consisting of small round punctures of about the same size as pronotal ones.All interstriae with sparse fine punctation, punctures about half the size of the strial ones; odd interstriae with large sparsely arranged dark-colored larger punctures (trichobotria), each with short indistinct seta only. Surface of elytra smooth in both sexes. Elytral apices in males and females simple, touching each other along suture even at very apex.

Ventrum. Mesoventral process reduced to a glabrous median ridge. Metaventrite with posterior elevation bearing medial groove; posterior part with short median projection, lateral projections absent. Abdominal ventrite I with very faint carina basally, without carina in posterior half. Ventrite 5 of both sexes with a wide, shallow apical notch delimited laterally by two distinct teeth slightly more produced in females. Margins of all abdominal ventrites smooth.

Legs. Basal pubescence on basal sixth of meso- and metafemora. Male protarsus with adhesive soles on tarsomere 1 which is only slightly thicker than tarsomeres 2–4; tarsomere 4 ca. as long as tarsomeres 1–3 combined. Claws slender, weakly curved.

Male genitalia. Total length 1.1 mm.Aedeagus laterally compressed. Basal piece ca. two-fifths of total aedeagus length. Paramere long, narrow, gradually acuminate, straightly projecting towards ventral side in lateral view; apices rounded, slightly bent mesally in dorsal view. Medi- an lobe slightly shorter than parameres, subcylindrical, its apical half much wider than apical half of paramere. Apex of median lobe acuminate forming a hook in lateral view. Larval morphology. In all external characters examined corresponding to the larva of B. muellerorum sp. nov. characterized below.

Differential diagnosis. Berosus pallidipennis can be recognized as distinct from B. muellerorum sp. nov. and B. halasi sp. nov. by the pronotum with large rectangular dark spot covering nearly the whole surface, basal half of femora black, elytral apices simple and closing tightly, and females with smooth elytral surface; the aedeagus is smallest of all New Zealand species, with straight parameres in lateral view and median lobe wide and nearly reaching parameral apices. Externally it is very similar to B. maru sp. nov. with which it may co-occur; males of both species can be easily recognized by the morphology of male genitalia, females may be recognized by different microsculpture of the elytra and different shape of the apical abdominal emargination. Habitat. Berosus pallidipennis inhabits a wide range of aquatic habitats, most frequently it is found along the vegetated river margins ( Fig. 3G ) and in side pools of stony rivers (with or without vegetation) ( Fig. 3H ). Less frequently it was found at margins and under stones in shallow mountain lakes with stony bottom, and only few findings come from standing vegetated pools outside of riverbeds.

Distribution ( Fig. 3D ). Widely distributed in the North Island (no records from Northland, Auckland, Coromandel and Taranaki) and South Island (no records from Mackenzie); the lack of records in the northern North Island may indicate that the species is absent from the northernmost New Zealand.

Figures

Fig. 1. External morphology of New Zealand Berosus, adults and larvae.A, E – B. pallidipennis (Sharp, 1884); B, F – B. maru sp. nov.; C–G, I–J, L – B. muellerorum sp. nov.; D–H, K – B. halasi sp. nov.; A–H – dorsal views; K–L – elytral apices; I–J – third instar larva (I – dorsal, semilateral and lateral view; J – head in dorsal view).

Fig. 2. New Zealand Berosus, details of adult morphology. A–D – coloration of meso- and metafemora; E–I – aedeagus in dorsal, lateral and ventral view; E–F – B. pallidipennis (Sharp, 1884) from North and South Island; G – B. muellerorum sp. nov.; H – B. halasi sp. nov.; I – B. maru sp. nov. The inset in grey: relative size of male genitalia of all species.

Fig. 3. Distribution and habitats of Berosus in New Zealand. A–D. Maps of examined specimens. E–H. Habitat photos of collection sited. E – shore of Lake Roundabout in Mid Canterbury, type locality of B. halasi sp. nov.; F – isolated rocky pools along Boyle River at Windy Point in North Canterbury, type locality of B. maru sp. nov.; G – pool at Wanaka Mount Aspiring Road in Otago Lakes, locality of B. pallidipennis (Sharp, 1884); H – exposed puddles in riverbed of Kahutara River at Inland Kaikoura Road in Kaikoura, locality of B. pallidipennis.